A federal court will hold a hearing Oct. 7 on the settlement. The Justice Department, which is also conducting a separate review of the antitrust implications of the settlement, has until Sept. 18 to file comments to the court.

The debate pits Google against tech rivals Microsoft and Amazon, who complain that the settlement would hand Google a dominant position in online book searches. Amazon's Kindle e-reader would directly compete with Google's book project.

The outcome will likely influence how books are searched a consumed in the future as titles move from paper to digital formats. Under the proposed settlement between Google, the Authors Guild and the Association of American Publishers, the search giant would have access to millions of books except those by authors who opt out of the settlement. Google argues that the deal will help spur research and give schools, the disabled and the underprivileged greater access to books.